One known method of recovering copper from copper ore is referred to as L-SX-EW process. In the L-SX-EW process, copper ore is leached with sulfuric acid or the like (L: Leaching), selectively recovering copper ions from leaching solution of copper by a solvent extraction (SX: Solvent Extraction), followed by, concentration, and electrolytic cathode copper is produced from this copper sulfate solution by an electrowinning (EW: Electrowinning).
In this process, among copper components contained in the copper ore, copper oxide ore may readily yield copper by a simple acid leaching. Moreover, among copper components contained in the copper ore, secondary copper sulfide ore such as chalcocite (Cu2S), and the like, is leachable by iron (III) ions. Therefore, copper can be efficiently leached by a ferric leaching process with the use of a solution containing iron (III) ions or a bacterial leaching process with the use of a microorganism which can oxidize iron (II) ions in the solution to iron (III) ions.
The ferric leaching process of the secondary copper sulfide ore is supposed to proceed according to the chemical reaction formula below (formula 1). Also, the bacterial leaching process is based on the same reaction mechanism with the ferric leaching process, characterized in continuously supplying an oxidant by consecutively oxidizing iron (II) ions, produced according to formula 1, into iron (III) ions with the aid of iron oxidizing microorganism.Cu2S+4Fe3+→2Cu2++4Fe2++S  (formula 1)
Among copper components contained in the copper ore, primary copper sulfide such as chalcopyrite (CuFeS2) may, however, be leached remarkably slowly by the simple acid leaching, the ferric leaching and the bacterial leaching. These methods have therefore been thought to be not suitable, since it takes an extremely long time to attain a high yield of copper leaching. If it would be granted that recovery of copper from the primary copper sulfide ore is not conducted, the yield of copper leaching will stay at a low level, and the economy is diminished anyway.
On the other hand, chalcopyrite is abundant in the copper ore, so that it has been desired to recover copper also from chalcopyrite in a highly efficient manner. There have therefore been proposed various techniques for improving the leaching rate in the process of leaching from the chalcopyrite-containing copper ore. Among them, a method of leaching by adding iodine (or iodide ion) and iron (III) ions has been known to improve the leaching rate from the chalcopyrite-containing copper ore, by feeding iodine as a catalyst in the form of dilute aqueous solution (Japanese Laid-Open Patent Publication Nos. 2010-024511 and 2011-042858).
In the method of leaching the chalcopyrite-containing copper ore, a method which is capable of reducing iodine loss without lowering the final yield of leaching has also proposed. In the method, two-stage leaching of the copper ore is a method that the copper oxide ore and secondary copper sulfide ore, which are soluble without iodine, are first subjected to leaching by the ferric leaching process or the bacterial leaching process based on a general oxidative leaching reaction (first leaching stage), and primary copper sulfide ore which is less soluble in the first leaching stage is then subjected to leaching in a solution containing iodide ion and iron (III) ion (second leaching stage). In the method, by using iodine only for leaching from the primary copper sulfide ore, the iodine loss could be minimized, while keeping the final yield of copper leaching (Japanese Laid-Open Patent Publication No. 2013-189687). It has also been proposed that the loss of iodine can be reduced not by mixing the leaching solution containing iron (III) ion with the leaching solution containing the iodide ion before being fed to a layer of stacked ores, but by feeding each leaching solution through routes independent of each other to the layer of stacked ores containing the copper sulfide ore (Japanese Laid-Open Patent Publication No. 2012-149316).